"Extra" data field on files

[Jono Spiro <jono%scribd.com@localhost>]

New to the group and libzip, but I've spent hours trying to answer this myself and have hit a wall:

Is there currently a way in libzip to write to the optional "extra" data field that is specified for a ZIP file header at offset 30+strlen(file name) (http://en.wikipedia.org/wiki/ZIP_(file_format)#File_headers)? I need to add an adler32 checksum here (DADA0400 followed by the checksum). I am streaming ZIP files into Flash and unzipping them as they download -- unfortunately the Flash player in the browser requires this checksum to be injected -- even if it's wrong.

Any help would be incredible!

Cheers,

Jono

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PS: On http://nih.at/libzip/: You should update "You can subscribe to it by sending a mail with the subject "subscribe libzip-discuss" to minimalist at nih.at." to read "at giga.or.at" -- since the other address doesn't work.